Particle theory

• Particles are held very tightly together in fixed position but they vibrate to and from • Particles in a solid has the least energy • Strong forces of attraction between particles. • Particles don’t move from their position so solids keep a definite shape and volume • Solids are not easily compressed because particles are packed very closely together • Solids are usually dense, as there are lots of particles in a small volume

• Particles are close together and they do stick together but they can move. free to move past each other, moving in all directions • Some forces of attraction between the particles • Liquids don’t keep a definite shape and can form puddles. They flow and fill the bottom of the container but keep the same volume • liquids won’t compress easily because the particles are packed closely together • Liquids are dense as there’s quite a lot of particles in a small volume

• Particles in a gas have the most energy • There are very weak forces of attraction between particles • Particles are far apart and free to move in all directions • Particles move fast, so they collide with each other and the container • Gases don’t have a definite shape or volume and will expand to fill the container. Gases can be compressed easily. Because there’s lots of free space between particles • Gases have very low densities, because there are not many particles in a large volume